1. Field of the Invention
The subject invention relates to a thermally air conditioned seat in an automotive vehicle by using air from the HVAC system of the vehicle.
2. Description of the Prior Art
The thermal comfort of passengers in a vehicle is conventionally provided by the central heating, ventilation and air conditioning (HVAC) module of the vehicle. Passengers are heated or cooled by convection through the surrounding medium in the interior of the vehicle. More recently, vehicle seating systems have been described that provide for dedicated heating and cooling of the occupant by an independent thermoelectrically energized unit incorporated into a vehicle seat. These units typically consist of one or more thermoelectric (TE) modules, heat exchangers, and fans, and are operated by allowing the fan to blow cabin air over the hot and cold sides of the thermoelectric, resulting in heat being absorbed from the air on the cold side and released to the air on the hot side. The cooled air is directed through or over the seat to the occupant's body surface, whereas the warmed air is rejected into the vehicle cabin, for instance under or behind the seat. Because these thermoelectrically climate controlled seats use cabin air as the medium, which generally is initially cold in heating mode and warm in cooling mode, there is necessarily a deliberate transient thermal response of the seating system.
The cooling and heating of a passenger in an automotive vehicle can most effectively be obtained by applying the thermal condition directly to the human being. The current automotive air conditioning systems utilize ducts at the floor to heat, and ducts leading to vents in the instrument panel to cool. The effectiveness in attempting to cool or heat occupants in an automobile is significantly lost to the surrounding air and thermal mass, as only part of the heat exchange is directed toward the passenger.
The optimum effect is attained by applying the conditioned air as directly as possible to the human passenger. This is accomplished by flowing conditioned air to the passenger seat from a known source like the HVAC module or a thermoelectric cooler/heater dedicated to the seat, as illustrated in U.S. Pat. No. Re. 38,128 to Gallup et al., U.S. Pat. No. 5,924,766 to Esaki et al., and U.S. Pat. No. 6,079,485 to Esaki et al., and PCT application WO 99/58907 to Bell.
However, the air from the HVAC module on initial startup is not thermally conditioned. In the case of heating, it takes time to warm the coolant due to the thermal inertia of the engine. In the case of cooling, it takes time for the typical Rankine A/C cycle to cool air. On the other hand, a dedicated thermoelectric device to heat or cool the ambient air from the vehicle cabin does have the thermal capacity vis-à-vis the electrical power available to provide optimum comfort. In other words, the electrical power required to energize the thermoelectric heat exchanger for adequate comfort is quite significant and sometimes not practical. In the heating mode, the passenger is not satisfied with the level of warmth. In cooling mode, the passenger is not satisfied with the cooling effect and even feels cold and clammy, as the thermoelectric does not dehumidify the air. The reason for this is that the dew point temperature is below the thermoelectric cooling temperature and little to no dehumidification takes place. When the humidity is very high in the passenger cabin, the thermoelectric device will collect condensed moisture without being able to eliminate it.